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  <div class="section" id="extending-via-numba-and-cffi">
<h1>Extending via Numba and CFFI<a class="headerlink" href="#extending-via-numba-and-cffi" title="Permalink to this headline">¶</a></h1>
<div class="highlight-python notranslate"><div class="highlight"><pre><span></span><span class="sa">r</span><span class="sd">&quot;&quot;&quot;</span>
<span class="sd">Building the required library in this example requires a source distribution</span>
<span class="sd">of NumPy or clone of the NumPy git repository since distributions.c is not</span>
<span class="sd">included in binary distributions.</span>

<span class="sd">On *nix, execute in numpy/random/src/distributions</span>

<span class="sd">export ${PYTHON_VERSION}=3.8 # Python version</span>
<span class="sd">export PYTHON_INCLUDE=#path to Python&#39;s include folder, usually \</span>
<span class="sd">    ${PYTHON_HOME}/include/python${PYTHON_VERSION}m</span>
<span class="sd">export NUMPY_INCLUDE=#path to numpy&#39;s include folder, usually \</span>
<span class="sd">    ${PYTHON_HOME}/lib/python${PYTHON_VERSION}/site-packages/numpy/core/include</span>
<span class="sd">gcc -shared -o libdistributions.so -fPIC distributions.c \</span>
<span class="sd">    -I${NUMPY_INCLUDE} -I${PYTHON_INCLUDE}</span>
<span class="sd">mv libdistributions.so ../../_examples/numba/</span>

<span class="sd">On Windows</span>

<span class="sd">rem PYTHON_HOME and PYTHON_VERSION are setup dependent, this is an example</span>
<span class="sd">set PYTHON_HOME=c:\Anaconda</span>
<span class="sd">set PYTHON_VERSION=38</span>
<span class="sd">cl.exe /LD .\distributions.c -DDLL_EXPORT \</span>
<span class="sd">    -I%PYTHON_HOME%\lib\site-packages\numpy\core\include \</span>
<span class="sd">    -I%PYTHON_HOME%\include %PYTHON_HOME%\libs\python%PYTHON_VERSION%.lib</span>
<span class="sd">move distributions.dll ../../_examples/numba/</span>
<span class="sd">&quot;&quot;&quot;</span>
<span class="kn">import</span> <span class="nn">os</span>

<span class="kn">import</span> <span class="nn">numba</span> <span class="k">as</span> <span class="nn">nb</span>
<span class="kn">import</span> <span class="nn">numpy</span> <span class="k">as</span> <span class="nn">np</span>
<span class="kn">from</span> <span class="nn">cffi</span> <span class="kn">import</span> <span class="n">FFI</span>

<span class="kn">from</span> <span class="nn">numpy.random</span> <span class="kn">import</span> <span class="n">PCG64</span>

<span class="n">ffi</span> <span class="o">=</span> <span class="n">FFI</span><span class="p">()</span>
<span class="k">if</span> <span class="n">os</span><span class="o">.</span><span class="n">path</span><span class="o">.</span><span class="n">exists</span><span class="p">(</span><span class="s1">&#39;./distributions.dll&#39;</span><span class="p">):</span>
    <span class="n">lib</span> <span class="o">=</span> <span class="n">ffi</span><span class="o">.</span><span class="n">dlopen</span><span class="p">(</span><span class="s1">&#39;./distributions.dll&#39;</span><span class="p">)</span>
<span class="k">elif</span> <span class="n">os</span><span class="o">.</span><span class="n">path</span><span class="o">.</span><span class="n">exists</span><span class="p">(</span><span class="s1">&#39;./libdistributions.so&#39;</span><span class="p">):</span>
    <span class="n">lib</span> <span class="o">=</span> <span class="n">ffi</span><span class="o">.</span><span class="n">dlopen</span><span class="p">(</span><span class="s1">&#39;./libdistributions.so&#39;</span><span class="p">)</span>
<span class="k">else</span><span class="p">:</span>
    <span class="k">raise</span> <span class="ne">RuntimeError</span><span class="p">(</span><span class="s1">&#39;Required DLL/so file was not found.&#39;</span><span class="p">)</span>

<span class="n">ffi</span><span class="o">.</span><span class="n">cdef</span><span class="p">(</span><span class="s2">&quot;&quot;&quot;</span>
<span class="s2">double random_standard_normal(void *bitgen_state);</span>
<span class="s2">&quot;&quot;&quot;</span><span class="p">)</span>
<span class="n">x</span> <span class="o">=</span> <span class="n">PCG64</span><span class="p">()</span>
<span class="n">xffi</span> <span class="o">=</span> <span class="n">x</span><span class="o">.</span><span class="n">cffi</span>
<span class="n">bit_generator</span> <span class="o">=</span> <span class="n">xffi</span><span class="o">.</span><span class="n">bit_generator</span>

<span class="n">random_standard_normal</span> <span class="o">=</span> <span class="n">lib</span><span class="o">.</span><span class="n">random_standard_normal</span>


<span class="k">def</span> <span class="nf">normals</span><span class="p">(</span><span class="n">n</span><span class="p">,</span> <span class="n">bit_generator</span><span class="p">):</span>
    <span class="n">out</span> <span class="o">=</span> <span class="n">np</span><span class="o">.</span><span class="n">empty</span><span class="p">(</span><span class="n">n</span><span class="p">)</span>
    <span class="k">for</span> <span class="n">i</span> <span class="ow">in</span> <span class="nb">range</span><span class="p">(</span><span class="n">n</span><span class="p">):</span>
        <span class="n">out</span><span class="p">[</span><span class="n">i</span><span class="p">]</span> <span class="o">=</span> <span class="n">random_standard_normal</span><span class="p">(</span><span class="n">bit_generator</span><span class="p">)</span>
    <span class="k">return</span> <span class="n">out</span>


<span class="n">normalsj</span> <span class="o">=</span> <span class="n">nb</span><span class="o">.</span><span class="n">jit</span><span class="p">(</span><span class="n">normals</span><span class="p">,</span> <span class="n">nopython</span><span class="o">=</span><span class="kc">True</span><span class="p">)</span>

<span class="c1"># Numba requires a memory address for void *</span>
<span class="c1"># Can also get address from x.ctypes.bit_generator.value</span>
<span class="n">bit_generator_address</span> <span class="o">=</span> <span class="nb">int</span><span class="p">(</span><span class="n">ffi</span><span class="o">.</span><span class="n">cast</span><span class="p">(</span><span class="s1">&#39;uintptr_t&#39;</span><span class="p">,</span> <span class="n">bit_generator</span><span class="p">))</span>

<span class="n">norm</span> <span class="o">=</span> <span class="n">normalsj</span><span class="p">(</span><span class="mi">1000</span><span class="p">,</span> <span class="n">bit_generator_address</span><span class="p">)</span>
<span class="nb">print</span><span class="p">(</span><span class="n">norm</span><span class="p">[:</span><span class="mi">12</span><span class="p">])</span>
</pre></div>
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